Second tank and AWC

Tastee · Sep 21, 2019

Hi all, I am planning to upgrade my RODI station and would love to hear any thoughts the good folk in the community have on my plans. I am based in Sydney Australia so apologies to those based in North America for some of the metric measurements. Apologies for the long post but I wanted to provide all the background and plans.

The current situation is as follows:

Split level house, timber floor on brick piers upstairs, concrete slab downstairs, 3’ drop from upper to lower. Fairly level block, slopes slightly front to back
Red Sea Reefer 250 tank inside the house (upstairs) controlled by a Neptune Apex, Apex located in the tank stand
Aquaforest Reef salt and 3 part dosing via Apex DOS heads
Custom made RODI station outside the house ~10’ away from the tank
Aquatic Life 100 GPD 4 stage RODI
Input TDS 70-120, town water supply @ 60 PSI
2 point TDS monitor - incoming supply and output after DI stage (TDS 1.in and 1.out)
Aquatic life RODI float valve and pressure sensitive solenoid kit (PSV)
100 litre reservoir, ~85 litres RODI when full
PMUP in reservoir automatically filling my Red Sea Reefer stock ATO once a day (Neptune ATK, connected to the tank Apex)
Eheim CompactON 3000 in reservoir, powered from inside the house, flexible 1” water line running inside to allow me to pump RODI inside the house whenever I want for WCs etc

I currently turn the RODI on manually every 2 or 3 weeks, allow it to fill and turn off via the PSV and then later on I turn the tap off. Water changes are performed manually inside the house using the RODI supply line (pump water into a barrel, mix salt, bring to temp, perform WC). I want to automate both processes. I am also planning to install a second Red Sea Reefer 525 XL in the house in the downstairs lounge ~40’ away from the RODI station. I want to run the same ATK solution to the new tank as well as the AWC.

The RODI auto fill would work this way

Replace the 100L RODI reservoir with a 240L reservoir
Repurpose the 100L reservoir as a SW mixing station
Install a power board (power strip) inside the RODI station
Install an FMM inside the RODI station and connect to the upstairs tank Apex
Install an Apex solenoid on the inlet line to the RODI (S1)
Re-mount the filters on the stock Aquatic Life mount
- Remove DI resin from mount and mount it separately further away on the right
- Remove the RO membrane and mount it in the DI resin mount
- This is to allow me to fit Tees inline in before and after the RO membrane and allow me to program a flush cycle to reduce TDS creep
Connect the Tee after the RO membrane to an Apex solenoid (S2)
FIT a second 2 way TDS meter reading before RO membrane (TDS 2.in) and downstream of S2 (2.out)
Fit an optical sensor ~1/2 way down the RODI reservior (O1)
Program the Apex to trigger RODI fill when O1 is open (see program below - I will rename the switch to something meaningful in the real program)

[RODIFill]
# This will control solenoid S1 aka RODIFill
Set OFF
If O1 OPEN Then ON
When ON > 600:00 Then OFF
Defer 001:00 Then OFF
Defer 001:00 Then ON

[TDSFlushOff]
Set OFF
If Output RODIFill = ON Then ON
Defer 002:00 Then ON

[TDSFlush]
# This will control solenoid S2 aka TDSFlush
Set OFF
If Output RODIFill = ON Then ON
If Output TDSFlushOff = ON Then OFF
When ON > 003:00 Then OFF

The AWC would work this way

Install 2 DOS units for AWC, one for each tank
Each DOS would be programmed to change the required amount of water in each tank, triggered after the mixing pump has been running for 30 mins
The SW mixing station will be calibrated to hold enough NSW for both WCs
Run twin RO lines to each tank, drawing from SW reservoir, wasting into sewer (conveniently next to the RODI station)
SW inlet lines will be secured at the bottom of the RODI reservoir, volume calibrated to leave ~50 mm/2” of NSW left over after an AWC
Install a second PMUP (NSWPump) in the RODI reservoir, connected to an auto shutoff float valve in the SW reservior (this is to fill the SW reservoir)
Install a mixing pump in the bottom of the SW reservoir pumping up (Eheim CompactON 600)
Install an optical sensor (O2) just below the auto shutoff (O2) (auto shutoff is just redundancy)
As soon as O2 is closed the mixing pump will start
Weigh the required amount of salt, walk outside and dump in the SW reservoir
Create a Virtual Outlet to start the AWC cycle and trigger manually or via Alexa
Apex program below

[AWC]
# This will normally be set to Off and I will change to Auto to trigger AWC
Set ON
When ON > 030:00 Then OFF # This will be tuned to be just > normal fill time

[NSWPump]
# This is the pump to fill the SW mixing station
Set OFF
If Output AWC = ON Then ON
If O2 CLOSED Then OFF
Defer 000:10 Then OFF

[MixingPump]
Fallback OFF
Set OFF
If O2 CLOSED Then ON

I currently change 15% of water in my tank every 6 weeks, around 28 litres. I plan to change a proportionally equivalent amount at the same frequency in the new tank once I have run it in. I want flexibility to change water more often in both tanks as needed (e.g. more often running the new tank in).

There are two aspects I would particularly like some feedback on:

Is an Eheim CompactON 600 a powerful enough mixer?
It is rated for 1m head height and would only be pushing ~750mm to the top of the SW reservoir, but that will be pumping open, without a hose, so I am concerned it won’t mix the top section. On the other hand I don’t want a geyser (-:
Any suggestions of solenoid setup apart from the Apex ones?
In Australia they will cost me ~A$150 each, A$75/solenoid and A$75/power supply. I’m not sure what other options I have in my current Apex setup. I will use the FMM 24v supply for the PMUP for the RODI fill, so need something else for the solenoids. I could buy an Apex break out box (BoB) and power irrigation solenoids from that but the BoB is A$100 so the saving will be small. I don’t think my EB6 and Apex 2016 base unit have anything inbuilt I can power a solenoid from.

Bramzor · Oct 9, 2019

This might be an idea for you.

For a cheaper version of AWC, you could use a high flow Dosing pump on 24V https://www.aliexpress.com/item/32948192564.html and put an extra dosing pump head on the same motor by buying 2 of them (so 1 motor, 1 speed, 2 heads = equal WC). Thats about 50$? You can trigger these dosing pumps using a FMM which can trigger a 24V and you can use the FMM ports for water leakage and water levels. I added my own DIY 2x Inductive Water sensor https://www.aliexpress.com/item/33041900609.html on that FMM to check RO water tank and Salt water tank from outside of the tank. (So no need to run wires inside which can corrode)
And I would use 1 port for water leakage detection (which you can also DIY so it would only cost like 5$). Leaving one additional sensor port.

To make sure that I would know if there is an issue. I would also use 3 Optical water sensors (https://www.aliexpress.com/item/32955443010.html) . 1 you can share with your Auto fill of RO to detect normal water level. The 2 others should be placed above and below that normal water level (Auto fill sensor) about half of the water volume you want to replace (or even lower). The 2nd sensor you put the same amount underneath the Auto fill sensor.
So you would trigger AWC once a day only when normal water level is reached (so the Auto Fill Sensor is high), level is lower than the High sensor and higher than the Low sensor. Making sure that if for some reason the AWC is pulling water out and not feeding in or the opposite or the difference of amount of water that is changed is higher than for example 1/2 of what you want to replace. It should also notify you and maybe even stop the water change. So if something would go wrong, you would be notified and can fix the partly done WC (which if done daily is only a 1-3% WC anyway)

So the cost of this AWC would be the cost of an FMM (and use 2 ports on a spare FMM), some cheap chinese high flow dosing pumps and sensors (which can all be DIY)
Myself I build my own Apex Neptune IR water level sensors, the more advanced inductive (no contact) water level sensors which Apex cannot provide and even the leak sensors where you can put a few leak sensors on 1 port by using cheap audio splitter. So should be doable to build full AWC for less than 250$ which is only a fraction of the cost that it would be using DOS + FMM + sensors.

To give feedback on your 2 questions.
1. I'm thinking of building a mixing container using magnetic stirrer instead of a pump. Sounds like a lot less maintenance and you can keep it running forever because it uses a lot less electricity too.
2. Solenoids you can DIY easily. You just buy the chinese RO water valve 24V (not sure if you need to NO normal open or NC normal closed version) Which is the same as the one from Apex. Personally I even added some LEDs so I could visually see if the Solenoid is triggered or not. Apex sells these 24V wires that you can attach to the FMM. The power supply you can also buy from China cause they only cost 10$. Break out box is something you cannot use to trigger a Solenoid, its only good for input signals as it sends out a low voltage (I think 3V) through a cable/sensor and checks if it gets the 3V on the other side which means the sensor is triggered.